Isoprene emission by plants in polluted environments

In recent years, anthropogenic activities and climate change have significantly increased exposure of plants to environmental stresses (single or multiple) and pollutants, which negatively affect plant growth, survival, and productivity. Plants may activate an armament of defenses against such environmental stresses. Isoprene, the most abundant biogenic volatile organic compound emitted by plants, is supposed to induce stress tolerance directly, by quenching reactive oxygen species, or indirectly by strengthening photosynthetic membranes and reprogramming expression of genes that are involved in antioxidant defense mechanisms. On the other hand, isoprene is also involved in tropospheric chemistry that contributes to the production of air pollutants when mixing with anthropogenic gases. In this review, we summarized current knowledge about the impact of air and soil pollutants on isoprene emission from plants, focusing on possible feedback and feedforward mechanisms that may affect whole ecosystem functioning and evolution of plant species. Despite limited available information, especially about long-term effects of soil pollutants, it may be speculated that isoprene generally improves fitness of plants challenged by air and soil pollutants, and their interaction with other organisms.